The subject disclosure relates generally to down-the-hole drill (“DHD”) hammers. In particular, the subject disclosure relates to a DHD hammer having an internal roller bearing assembly between a drill bit and a chuck.
Typical DHD hammers involve a combination of percussive and rotational movement of the drill bit to drill or chip away at rock. Such DHD hammers are powered by a rotatable drill string attached to a drilling platform that supplies rotation and high pressure gases (e.g., air) for percussive drilling. Moreover, in percussive drilling, rock cutting is a result of percussive impact forces rather than shear forces. In other words, rotation of the DHD hammer serves to rotationally index the drill bit to fresh rock formations after the drill bit impacts a rock surface rather than to impart shear cutting forces to the rock surface.
Such DHD hammers typically include an internal bearing for maintaining the drill bit centrally aligned about the DHD hammer's central longitudinal axis. However, such internal bearings are typically only designed to provide axial alignment and are not capable of carrying substantial side loads which leads to a relatively short life span for such components.